The Principle and Application of Single Screw Extruder


Ningbo Fangli Technology Co., Ltd. is a mechanical equipment manufacturer with nearly 30 years’ experiences of plastic pipe extrusion equipment, new environmental protection and new materials equipment. Since its establishment Fangli has been developed based on user’s demands. Through continuous improvement, independent R&D on the core technology and digestion & absorption of advanced technology and other means, we have developed PVC pipe extrusion line, PP-R pipe extrusion line, PE water supply / gas pipe extrusion line, which was recommended by the Chinese Ministry of Construction to replace imported products. We have gained the title of “First-class Brand in Zhejiang Province”.


As a common extruder equipmentthe single screw extruder is used in plastic processing industry. What is its principle and structure? Below is the analysis for the single screw extruder from the extruder conveying section, compression section and metering section.

The effective length of single screw extruder is generally divided into three sections. Three effective sections are determined according to the screw diameter, screw distance and screw depth, which are generally divided into one third each.

High efficiency single screw extruder adopts two-stage overall design, strengthens plasticizing function, ensures high-speed, high-performance and stable extrusion. Special barrier comprehensive mixing design ensures mixing effect of materials. High shear and low melt plasticizing temperature ensures high-performance, low temperature and low pressure metering extrusion of materials. The design concept and features are that high speed and high yield extrusion bases on high straight level.


The principle of single screw extruder

A thread behind the feed port is called the conveying section. The material here is required not to be plasticized, but to be preheated and compacted under pressure. In the past, the old extrusion theory thought that the material here is loose. Later, it was proved that the material here is actually a solid plug, that is to say, the material here is solid like a plug after being extruded. Therefore, as long as the conveying task is completed, its function is done.

Principle of single screw extruder: The second section is called compression section, the volume of screw groove gradually decreases from large to small, and the temperature should reach the degree of material plasticization. The compression produced here is from conveying section 3 to 1, which is called the compression ratio of screw - 3:1. Some machines also change, and the plasticized material enters into the third section.

Principle of single screw extruder: the third section is the metering section, where the material maintains the plasticizing temperature, just like the metering pump, the melt material is accurately and quantitatively transported to the die head. At this time, the temperature can not be lower than the plasticizing temperature, generally slightly higher.

The single screw extruder is mainly used for extruding soft, hard PVC, polyethylene and other thermoplastic plastics. It can process a variety of plastic products, such as film, pipe, plate, ribbon, etc., and can also be used for granulation in combination with corresponding auxiliary machines (including molding head).

The plastic extruder has the advantages of reasonable design, high quality, good plasticization, low energy consumption, low noise, stable operation, large bearing capacity and long service life.


Application of single screw extruder

Pipe extrusion: suitable for PP-R pipe, PE gas pipe, PEX cross-linking pipe, aluminum plastic composite pipe, ABS pipe, PVC pipe, HDPE silicon core pipe and various co-extrusion composite pipes.

Sheet and sheet extrusion: suitable for PVC, pet, PS, PP, PC and other profiles and plates extrusion, as well as other kinds of plastics extrusion, such as wire, rod, etc.

Extrusion of profile: adjust the speed of extruder and change the structure of extrusion screw, which can be used to produce PVC, polyolefin and other plastic profiles.

Modified granulation: suitable for blending, modification and strengthening granulation of various plastics.


If you need more information, Ningbo Fangli Technology Co., Ltd. welcomes you to contact for a detailed inquiry, we will provide you with professional technical guidance or equipment procurement suggestions.

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